The long-running crime drama continues its 14th series. In this week’s episode, a recently exonerated felon is accused of murdering a vilified baseball player, dredging up a 20-year-old murder case involving a detective with a grudge.

Detectives Briscoe and Green are called to a disreputable bar where baseball player Brendan Donner has been murdered by a blow to the head with a whisky bottle. Donner had recently cost his New York side the League Championship Series. “The suspect list is the Greater New York phonebook,” mutters Briscoe. The cops discover that Donner recently split with his wife after he became obsessed with reading the sackfuls of hatemail he was receiving on a daily basis. However, none of the more sinister threats Donner received point to an obvious suspect.

It is not until the lab finds prints on the murder weapon belonging to one Walter Grimes that the detectives are offered a breakthrough. Grimes was recently released from prison after serving 20 years for a murder he did not commit. He was found guilty of stabbing a girl to death in the 1980s, but his lawyer Rodney Fallon – who specialises in exonerating those he believes to be innocent – recently had his client released after proving that the blood on the knife did not belong to the girl in question. However, as well as the prints on the bottle, the detectives have eight witnesses who claim to have seen a man who fits Grimes’s description attack Donner.

The detectives track down their suspect, who tries to take a bystander hostage when he sees the cops approaching. In custody, Grimes says that he acted in self-defence against Donner who had turned on him for no reason – possibly because the paranoid sportsman was expecting someone to attack him at any moment. He and the aggressive Fallon claim that prison turned an innocent man towards irrational violence. “I’m sorry the system failed you, Mr Donner,” says McCoy. “But a wrongful conviction doesn’t earn anyone a free pass on murder.” Psychiatrist Dr Olivet examines the suspect, and although deeming him to be perfectly sane, she does believe that he had difficulty adjusting to his newfound freedom.

Was Grimes an innocent man before prison? His juvenile police records show that he was involved in a string of offences, from assault to armed theft. A cop called Kenny Daniels – an old friend of Green’s – tried to charge Grimes with holding up a liquor store some years earlier, even though the store owner swears the crime was committed by someone else. However, despite Daniels’s efforts, Grimes was never prosecuted for this or for any other of his nascent crimes. Daniels, though, was also involved in the subsequent murder that Grimes was accused of committing.

Green discovers that Daniels knew Grimes was innocent of this particular murder, but had killed a different teenage girl, Julie Sayer. After his superior saw that Daniels had beaten his suspect, he allowed Grimes to walk free. Daniels admits to planting the bloody knife – covered in Grimes’s fingerprints – back into Grimes’s apartment when a similar murder occurred in order to see him punished for murder. “It was eating me up, Ed,” confesses Daniels. “I had to make it right – I had to balance the scales.”

Fallon is incensed that his client has been the victim of a supposed grudge. However, DNA evidence – that was not available in the 1980s – now proves that the blood on the knife did indeed belong to Julie Sayer. McCoy and Southerlyn believe that despite Daniels’s underhand tactics, the fact that Grimes did kill proves that he was predisposed to violence before his prison experience could affect him. Will the jury concur and find Grimes guilty of both murders?